Adenovirus-medicated suicide gene therapy is an investigation cancer therapy that has produced impressive results in preclinical models. Despite these promising results, this approach has shown limited efficacy in the clinic largely due to a low efficiency of gene transfer in vivo. To overcome this limitation, our research program has developed a novel, trimodal approach that utilizes an oncolytic, replication-competent adenovirus to selectively and efficiently deliver a pair of therapeutic suicide genes to tumors. Preclinical studies have demonstrated that the replication-competent adenovirus itself generates a potent anti-tumor effect. The therapeutic efficacy of the adenovirus can be enhanced significantly by invoking two suicide gene systems (CD/5-FC and HSV-1 TK/GCV), which render malignant cells sensitive to specific pharmacological agents and, importantly, sensitizes them to radiation. Two phase I clinical trials that evaluated the safety and efficacy of replication-competent adenovirus-mediated double suicide gene therapy without (BB-IND 8436) and with (BB-IND 9852) three-dimensional conformal radiotherapy (3D-CRT) in men with prostate cancer have been completed with excellent results. The results demonstrate that replication-competent adenovirus-mediated double suicide gone therapy can be combined safely with conventional dose 3D-CRT and is showing signs of biological activity. This Program Project builds on our previous preclinical and clinical accomplishments with a single-minded goal- to develop the technology of replication-competent adenovirus-mediated double suicide gene therapy to a point where it will be a safe and effective adjuvant to radiation therapy in the clinic. To accomplish this, we have assembled a highly interactive group of projects and cores that function as a comprehensive and cohesive unit that will advance gone therapy technology on three fronts: 1) by developing better adenoviral vectors and therapeutic genes, 2) by developing better means of vector delivery and monitoring of therapeutic gone expression in vivo, and 3) by evaluating the merit of these preclinical advancements in three Phase I/II clinical trials. The combined basic and clinical science described here will generate new important knowledge and may ultimately lead to more effective cancer treatments.